When networks are fed by several interconnected sources, an interconnection circuit-breaker must be able to break short-circuit current which is the sum of the currents discharged by several of these sources. This is why it has been sought to reduce the magnitude of the cut-out currents borne by the circuit-breakers in such installations.
Thus, in an installation comprising a generator connected to two high-voltage transformers ensuring an interconnection between two networks, such as that which is the object of U.S. Pat. application No. 713,474 of Aug. 11, 1976, the protection device used allows a reduction in the cut-out powers of the circuit breakers of the generators, but the initial short-circuit current is passed for a relatively long time.
Indeed, generator circuit-breakers have a high rated current and are generally air-insulated devices. They include heavy moving contacts with relatively long strokes and a fairly long operation time results therefrom.
Now, when a fault can draw current from different interconnected sources, it is advantageous to:
Reduce very rapidly the power supply supplied by at least one of the sources, preferably the most powerful, in order to limit the damage caused by a high short-circuit current; PA1 Maintain the stability of the network and the synchronization between the sources by the insertion of a connection resistor, generally a resistor with a fairly low ohmic value; and PA1 Reduce the duration of the current flow in the connection resistor in order to reduce the energy dissipated in this resistor and consequently its bulk.